Metastatic Malignant Mesothelioma of the Tunica Vaginalis Testis Treated With Sequential Immunotherapy, Chemotherapy, and Radiotherapy With Prolonged Disease Stabilisation: A Case Report.

We report the case of a 77-year-old man with no known history of asbestos exposure who presented with a right-sided hydrocele. Histopathological analysis following hydrocele repair identified epithelioid-type malignant mesothelioma of the tunica vaginalis testis. Staging investigations confirmed disease confined to the hemiscrotum, and definitive management included right inguinal orchidectomy, excision of the spermatic cord to the deep inguinal ring, and wide local excision of the involved scrotal tissue. Initial surveillance imaging showed no recurrence, but nodal metastatic disease subsequently developed. The patient received first-line immunotherapy with ipilimumab and nivolumab but experienced progressive nodal disease. Second-line carboplatin-pemetrexed chemotherapy resulted in a mixed radiological response after three cycles, with para-aortic nodal oligoprogression managed using palliative radiotherapy. Following palliative radiotherapy and three further cycles of carboplatin-pemetrexed chemotherapy, imaging demonstrated a partial radiological response. Further surveillance revealed thoracic and intra-abdominal nodal progression, which was managed with a second course of palliative radiotherapy and was followed by renewed disease stabilisation. Subsequent progression involved pulmonary and intra-abdominal nodal disease, prompting initiation of third-line oral vinorelbine. Imaging demonstrated predominantly stable disease with isolated para-aortic oligoprogression, which was treated with a third course of palliative radiotherapy, after which vinorelbine was resumed. Approximately four years after diagnosis, the patient remained clinically stable, with an Eastern Cooperative Oncology Group (ECOG) performance status of 1, and was awaiting interval imaging to assess radiological disease status. This case illustrates that an individualised sequential treatment strategy incorporating immunotherapy, chemotherapy, and palliative radiotherapy to sites of oligoprogression may be associated with periods of disease control in metastatic malignant mesothelioma of the tunica vaginalis testis.